1. Field of the Invention
The present invention relates to a display medium capable of displaying an image by applying an electric field to fluid material sealed in a fluid chamber.
2. Description of the Related Art
In a display medium, such as a liquid crystal display device or an electrophoretic display device having a fluid chamber formed between two opposing substrates, image quality suffers when air bubbles enter the fluid material, such as the liquid crystal or electrophoretic medium, sealed in the fluid chamber. Various technologies have been proposed for preventing air bubbles from getting into the fluid material.
For example, a liquid crystal display cell is proposed in Japanese unexamined patent application publication No. 2004-117523. The liquid crystal display cell is formed with no residual air bubbles and no unfilled areas by providing a plurality of injection ports for injecting a liquid crystal material, and by providing exhaust ports in regions where the liquid crystal material injected through the injection ports is slow to arrive.
Japanese unexamined patent application publication No. HEI-11-249155 proposes a method for producing a fluid material injected structure, such as a liquid crystal device. The method includes arranging a pair of substrates in confrontation with each other, after applying a liquid crystal or other fluid material to one of the substrates, holding the substrates at a prescribed distance from each other using noncontact holding means, and subsequently releasing the held state of the substrates so that the pair of substrates is gradually pressed together from one edge to the opposing edge, flattening the fluid material in the sealed region.
However, with the technology disclosed in Japanese unexamined patent application publication No. 2004-117523, there have been difficulties in reliably predicting the flow of injected liquid crystal material in order to provide the exhaust ports in the appropriate locations. Hence, after providing exhaust ports at locations based on the predicted flow of liquid crystal material, the liquid crystal material did not always flow as predicted due to the conditions at the time of injection, resulting in air bubbles produced in the liquid crystal material.
Further, since the liquid crystal display cell according to this technology is provided with a plurality of openings, i.e. the injection ports and the exhaust ports, the risk of air bubbles entering the cell during or after sealing these openings is high.
On the other hand, the method of bonding the two substrates via a fluid material disclosed in Japanese unexamined patent application publication No. HEI-11-249155 is effective when the fluid material injected structure (hereinafter referred to as a “display medium”) is a liquid crystal cell for a liquid crystal display device since the fluid material is a liquid crystal containing no particles. However, when the display medium being produced is a display panel for an electrophoretic device, the fluid material is a charged particle dispersion fluid containing charged particles. Hence, bonded areas of the substrates became contaminated by charged particles, compromising the bonds between the substrates and allowing air bubbles to enter after the substrates have been sealed.